Analysis of a collection of Escherichia coli isolates recovered from beach waters on the coast of the Río de la Plata in Montevideo.

Antibiotic resistance has become a global and multidimensional problem, where the capacity for environmental dispersion is one of the most important aspects. Estuaries are usually hotspots for anthropogenic impact because they receive effluents from wastewater treatment plants. This constitutes a potential health risk when they are used for recreational activities. Río de la Plata is an estuarine system in South America, located south of Uruguay, on whose western margin lies Montevideo, the capital of this country. In the coastal area of Montevideo, the estuary receives effluents from the city's sewage system, after treatment that lacks a process to reduce microbial content. In this work, a small collection of Escherichia coli, a classic indicator microorganism for fecal contamination of water, was recovered from three beaches of Montevideo. Most of them were resistant to different antibiotics, and the ability for conjugative transfer of resistance genes was verified in some cases, alongside the analysis of the mobile genetic elements involved. Phylogenetic profile, preliminary virulence content, and bacteriocin production of the isolates were also determined. This would be the first report that broadly characterizes a collection of E. coli isolated from the coast of Río de la Plata. Considering that the beaches of Montevideo are used for recreation, it would be important to monitor the abundance of antibiotic-resistant bacteria and their corresponding genes in coastal areas of the city. This would provide information on the spread of antibiotic resistance in this environment and consequently, on the potential risk for human health.